What does the police killing of a homeless man in San Francisco have to do with the Arab Spring uprisings from Tunisia to Syria? The attempt to suppress the protests that followed. In our digitally networked world, the ability to communicate is increasingly viewed as a basic right. Open communication fuels revolutions—it can take down dictators. When governments fear the power of their people, they repress, intimidate and try to silence them, whether in Tahrir Square or downtown San Francisco.

Charles Blair Hill was shot and killed on the platform of the Bay Area Rapid Transit (BART) system’s Civic Center platform on July 3, by BART police officer James Crowell. BART police reportedly responded to calls about a man drinking on the underground subway platform. According to police, Hill threw a vodka bottle at the two officers and then threatened them with a knife, at which point Crowell shot him. Hill was pronounced dead at the hospital.

Hill’s killing sparked immediate and vigorous protests against the BART police, similar to those that followed the BART police killing of Oscar Grant on New Year’s Day 2009. Grant was handcuffed, facedown on a subway platform, and restrained by one officer when another shot and killed him with a point-blank shot to the back. The execution was caught on at least two cellphone videos. The shooter, BART officer Johannes Mehserle, served just over seven months in jail for the killing.

On July 11, major protests shut down the Civic Center BART station. As another planned protest neared on Aug. 11, BART officials took a measure unprecedented in U.S. history: They shut down cellphone towers in the subway system.

“It’s the first known incident that we’ve heard of where the government has shut down a cellphone network in order to prevent people from engaging in political protest,” Catherine Crump of the ACLU told me. “Cellphone networks are something we’ve all come to rely on. People use them for all sorts of communication that have nothing to do with protest. And this is really a sweeping and overbroad reaction by the police.”

The cellular-service shutdown, which was defended by BART authorities who claimed it was done to protect public safety, immediately drew fire from free-speech activists around the globe. On Twitter, those opposed to BART’s censorship started using the hashtag #muBARTak to make the link to Egypt.

When the embattled Egyptian dictator Hosni Mubarak shut down cell service and the Internet, those in Tahrir Square innovated workarounds to get the word out. An activist group called Telecomix, a volunteer organization that supports free speech and an open Internet, organized 300 dial-up phone accounts that allowed Egyptian activists and journalists to access the Internet to post tweets, photos and videos of the revolution in progress.

“We were very active—Tunisia, Egypt, Libya, Syria—trying to keep the Internet running in these countries in the face of really almost overwhelming efforts by governments to shut them down,” Telecomix activist Peter Fein told me. “Telecomix believes that the best way to support free speech and free communication is by building, by building tools that we can use to provide ourselves with those rights, rather than relying on governments to respect them.”

Expect hacktivist groups to support revolutions abroad, but also to assist protest movements here at home. In retaliation for BART’s cellphone shutdown, a decentralized hacker collective called Anonymous shut down BART’s website. In a controversial move, Anonymous also released the information of more than 2,000 BART passengers, to expose the shoddy computer security standards maintained by BART.

The BART police say the FBI is investigating Anonymous’ attack. I interviewed an Anonymous member who calls himself “Commander X” on the “Democracy Now!” news hour. His voice disguised to protect his anonymity, he told me over the phone: “We’re filled with indignation, when a little organization like BART ... kills innocent people, two or three of them in the last few years, and then has the nerve to also cut off the cellphone service and act exactly like a dictator in the Mideast. How dare they do this in the United States of America.”

Amy Goodman is the host of “Democracy Now!,” a daily international TV/radio news hour airing on more than 950 stations in North America. She is the author of “Breaking the Sound Barrier,” recently released in paperback and now a New York Times best-seller.